In recent years, demand for portable electronic products such as notebook computers, video cameras, portable telephones and the like has been drastically increased and electric vehicles, storage batteries for energy storage, robots, satellites and the like have been actively developed. For this reason, high performance secondary batteries capable of repeated charge and discharge have been actively studied.
Lithium secondary batteries currently commercially available include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries and lithium secondary batteries. Among them, the lithium secondary batteries are in the spotlight because they have almost no memory effect compared to nickel-based secondary batteries, and thus perform charge and discharge freely, have very low self-discharge rate and have high energy density.
A secondary battery is attracting attention as a new energy source for improving environment-friendliness and energy efficiency in that it has not only a primary advantage of greatly reducing the use of fossil fuels but also a secondary advantage of generating no by-products due to the use of energy.
Korean Unexamined Patent Publication No. 10-2015-0027510 (hereinafter, referred to as a conventional literature) discloses such a secondary battery as a conventional art. FIG. 1 is a schematic view showing an electric vehicle disclosed in the conventional literature.
Referring to FIG. 1, an electric vehicle 10 includes a pre-charge and voltage supply system 30, a DC-AC inverter 40, a vehicle motor system 50, a vehicle controller 52 and the like. The system 30 includes a first battery 60, a voltage sensor 70, a contactor 80, a contactor driver 90, a voltage sensor 110, a DC-DC voltage converter 120 and a second battery 130. The first battery 60 is configured to supply power for driving the vehicle motor system 50. The second battery 130 is configured to supply power for pre-charging a capacitor in the DC-AC inverter 40.
However, the electric vehicle 10 disclosed in the conventional literature essentially includes the second battery 130 for pre-charging a capacitor in the DC-AC inverter 40, which increases the cost and limits the space. Moreover, the conventional literature fails to suggest a technique for emergency control of the electric vehicle 10 while the contactor 80 is abnormally operating.